A hash algorithm is a function which takes a variable size input and produces a fixed size output. The algorithm tries to make it difficult to predict the output for a given input, find two inputs with the same output, or reconstruct the input from the output.

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80
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9answers
14k views

Does anybody not store salts?

We talked about password hashing and salting in class today. Our professor had a very different understanding of the use case of salts from mine and said that you might not store the salt at all and ...
3
votes
4answers
933 views

Convert SHA-256 to SHA-1 and MD5 - Increase bit length/entropy?

I know this is a real dumb question and I am certainly talking complete rubbish, but let me explain: We have a long SHA-256 hash, e.g.: ...
-3
votes
6answers
587 views

Is this password hashing method secure?

I have made a custom hashing method to help make my users' passwords more secure if the database will be leaked. The encryption method is like this: A method takes an input of 1 character, gets the ...
3
votes
1answer
72 views

Recommended Crypto Security Setup (Implemented Algorithms)?

Firstly I'm not a crypto expert, however I know how to use algorithms that other people have defined before in practical usages, that is, as long as they live up to their promises. The thing is that ...
3
votes
2answers
97 views

Does a hash of a 32-bit integer make a better hash salt than the integer itself?

I have a scenario where I already have a table of resource passwords stored as unsalted 128-bit hashes. I'm unable to force owners to provide new passwords, so I'm trying to mitigate the situation by ...
12
votes
5answers
2k views

What is the best way to transmit password hash over unreliable TLS?

I have TLS connection between my server and client. I have no certificate, so the connection is susceptible to the Man-in-the-middle attack. I fear that attacker could intercept the password hash ...
1
vote
0answers
50 views

Create reduction functions in rainbow tables

I have been trying to understand rainbow tables lately and one part is giving me trouble to understand here. Let's say I want to generate a table where the chains are 100 000 hash/plaintext long. I ...
5
votes
3answers
26k views

What are the differences between dictionary attack and brute force attack?

Can someone explain the major differences between a Brute force attack and a Dictionary attack. Does the term rainbow table has any relation with these?
1
vote
3answers
295 views

About SHA1 in default Disk Encryption in Linux

Link to the thread: Recommended options for LUKS (cryptsetup) I wonder what's the exact difference between SHA1 and SHA512. I know that SHA512 has a longer key but I've read that it doesn't matter ...
1
vote
3answers
145 views

Is hashing passwords with bcrypt and a constant salt more unsecure than SHA1?

I've built an API that allows users to submit encrypted data to be stored in the cloud. To retrieve their data, the API requires the user to supply only the MongoDB Object ID that they are given when ...
8
votes
3answers
608 views

How secure is HTTPS with weak ciphersuites?

Today I came across the website https://mtgox.com/, which claimed to be secure because of the Verisign certificate. I checked the certificate out of curiosity (it's the first thing they claim, let's ...
1
vote
0answers
104 views

Find salt from md5 hash if password is known

I have a salted MD5 hash and I also know the password. How can I recover the salt using tools like John The Ripper (I have JTR jumbo installed)?
-4
votes
1answer
1k views

Please tell me two strings which have the same MD5 hash value

Yes, I know MD5 is weak and should not be used. To make a prove of concept I need two strings with the same MD5 value but all I can find is binary. Like this nice example. Works fine as binary but ...
0
votes
1answer
51 views

Setoolkit - credential harvester, only display the first character of the password

I'm launching a spear phishing campaign and my client has specifically asked me to only harvest the first character of the password, is there a way to do so? Basically instead of showing the whole ...
1
vote
2answers
2k views

Extract Password Hashes from Active Directory LDAP

Currently we are working on a monthly internal security test which among other should contain a verification of the real password strength the users choose. For this reason I want to extract the ...
1
vote
0answers
33 views

Using hash of root password to encrypt files/folders (Debian 8 Linux)

I have an application that requires unattended decryption of files/folders. Would it be possible to utilize the hash of the root password to prevent an attack where a malicious user changes the root ...
16
votes
3answers
1k views

Does it make sense to choose a longer password than the output of a hash?

Let's take MD5 for example: It outputs a 128-bit hash. Does it make sense (in theory) to choose an input (password) which is itself longer than 128-bit? Does it increase the probability of a ...
3
votes
2answers
74 views

Would a Password Using All Possible Unicode Code Points Cause Problems in Traditional Hashing Algorithms, such as Bcrypt?

I've been toying around with this idea, but hypothetically, if you had a password manager that would use any possible renderable (e.g. not control characters such as BEL, NUL, DEL, etc., or surrogate ...
-2
votes
3answers
148 views

Is it possible to reverse MD5? [duplicate]

I'm new in the security world and right now I'm studying about hashes. Let's say I have md5(x+q) and md5(y+q). I know the value of x and y hidden into md5. Would it be possible to reverse it and ...
2
votes
1answer
241 views

Encrypting data before sending to SaaS tool and decrypting on browser view

I'd like to send data to a SaaS tool, where the data is stored in the cloud. I'll use Google Analytics as an example, but it applies to any similar service. Google Analytics does not allow you to ...
-4
votes
1answer
83 views

Does combining two encrypted strings secures password? [duplicate]

For example, a person having password 123456. it's MD5 is e10adc3949ba59abbe56e057f20f883e and SHA1 is 7c4a8d09ca3762af61e59520943dc26494f8941b and after joining both hashes. Which comes to be ...
0
votes
2answers
117 views

Why is it a problem to store strong passwords as unsalted hashes?

My users all have strong (80-bit true entropy) passwords. How do I know that? Because my imaginary website randomly generates the passwords for them (client-side). In that context, could you explain ...
3
votes
1answer
50 views

Help converting string to NTLM

I'm trying to covert a string into a NTLM hash. From what I understand you just have to covert the characters in the string to unicode, format it to little endian and then hash it with the MD4 ...
148
votes
5answers
22k views

Does Facebook store plain-text passwords?

I was about to reset my Facebook password and got this error: Your new password is too similar to your current password. Please try another password. I assumed that Facebook stores only password ...
3
votes
1answer
1k views

How does Windows Server 2008 store local users' passwords?

It is not clear to me how Windows Server 2008 R8 stores local account passwords. Is there any salt added or just NT hash is computed and stored? The following article describes all the methods used ...
1
vote
1answer
46 views

Should I verify installer file PGP hash?

Let's say that I'll download an installer for a program on Windows and the publisher has released PGP Signature for the file. The installer file does not have any code signing certificates. If I ...
1
vote
3answers
45 views

Why are there Hashes next to downloads? [duplicate]

I've seen several sites wehre they would put the hash of the downloadable file next to the file. Why do they do this ? I understand the purpose of comparing the hash of your file with the online hash ...
-12
votes
1answer
85 views

I have an MD5 encrypted link. How do I decrypt? [closed]

I have this MD5 hash of a link: 687474703a2f2f696d6775722e636f6d2f45554a43734742 I only have this code, no other information. How can I crack it?
4
votes
1answer
295 views

OpenSSL 0.9.6a PRNG algorithm weakness: How to exploit?

I saw an OpenSSL security advisory for Openssl 0.9.6a Recently a cryptographic flaw in OpenSSL's built-in pseudo-random number generator (PRNG) was pointed out to us by Markku-Juhani O. Saarinen , ...
2
votes
3answers
292 views

How can Alice and Bob prove that they share a file?

Carl asks Alice and Bob if they have a file f such that for a secure cryptographic hash function h, h(f) = K. Both claim to have f, but they can't show the file. Carl doesn't believe them. He can ...
-3
votes
1answer
103 views

How to get secure hashing software? [closed]

I am searching for an open source hash calculator that I can download to verify my Tails .iso image, but I also want to be able to to calculate some password hashes with a sha512 hash (which is why I ...
2
votes
2answers
60 views

Using a hash in place of user data

I'm storing client data and they are sensitive about privacy and security of the data. In some cases, I don't need the actual data, but could work with a hash of the data. For example, in the case of ...
3
votes
1answer
77 views

Besides Browsers, what other Technologies are Impacted by the Deprecation of SHA-1?

I am aware that from January 2017, browsers will start rejecting, or at least warning, users browsing sites offering SHA-1-signed certificates. Would a service be impacted if the system does not ...
-6
votes
2answers
53 views

How to brute force this token in php, if it is possible

it is possible to brute-force this token (MD5 Hash) of the following script (PHP) in a realistic time (0,5h - 24h)? If the answer is YES, how could I do it, for example with PHP or Python? $time = ...
2
votes
0answers
12 views

hash function notations and existing cryptographic hash algorithms [migrated]

I am implementing Role-based access control by referencing the paper Enforcing Role-Based Access Control for Secure Data Storage in the Cloud. In page 6, they have mentioned to choose hash functions ...
0
votes
4answers
98 views

How are salts safe in the database? [duplicate]

I have read many and many of this type of question on the security stack community before I asked this question, but one thing that made me mad about salts and saving it in database is this ... I will ...
10
votes
4answers
8k views

HMACSHA512 versus Rfc2898DeriveBytes for password hash

We are currently using HMACSHA512 in .net, with a 128Char (64byte) validation key The salt is 64 char randomly generated string. We allocated 2048 length on the database for the hashed base64 string ...
4
votes
2answers
566 views

Keepass Dictionary Attack Protection Strategy

Though pretty interested, I'm everything but an expert in Information Security, please redirect me to any helpful resources if my question is stupid or correct me if my assumptions are wrong. When ...
72
votes
13answers
6k views

VP of IT claims he unhashed 100% of all 16k employees' PWs. Is he lying to us?

I work for a company which has ~16,000 employees. Periodically, our VP of IT sends out a newsletter with "tech-tips" and misc IT stuff. The topic of this week's newsletter was "password security". ...
2
votes
0answers
93 views

Any vulnerability in .net implementation for C# object.GetHashCode?

I've already asked this question on SO, but I think that this forum is more appropriate to discuss security issues. My point is that most OO languages has a way to get a unique hash code for an ...
26
votes
2answers
2k views

How can the content of a file refer to its own MD5?

So I just saw this picture on Imgur: http://imgur.com/gxRCrCM The intriguing thing about it is that the picture refers to an old Daft Punk song named "Face 2 Face". The image's MD5 is ...
0
votes
2answers
100 views

How secure is the hashing/salting/stretching process as described in this diagram?

Question I was just brainstorming about the hashing, stretching, salting part of the user password in the authentication process and I want it to be as secure as possible (no matter how paranoid that ...
7
votes
1answer
127 views

What are the recommended scrypt cost factors for 2016?

I've been trying to look for the answer, but the latest one I found was outdated by three years. So what are the recommended scrypt cost factors for 2016?
1
vote
1answer
75 views

How secure is the UNIX sha_crypt as a password storage algorithm? [duplicate]

So I have been working on password storage, especially on the algorithms to use (and to not use). Most people are recommending scrypt or PBKDF2 for valuable reasons, but I have not seen any talks ...
-1
votes
2answers
135 views

How long would it take to generate a file to match a hash? [duplicate]

A individual file only has a single hash of any specific byte length. But an individual hash can represent a large number of different files. Given a 256 byte hash, how long would it take to ...
-1
votes
2answers
77 views

Website says my new password can't be used because it is the same as an old one [duplicate]

What are the risks of storing (in hashes I guess) all the old passwords? Why would a company chose to not delete old passwords? Why not let users reuse old passwords?
124
votes
6answers
47k views

Password Hashing add salt + pepper or is salt enough?

Please Note: I'm aware that the proper method for secure password storage hashing is either scrypt or bcrypt. This question isn't for implementation in actual software, it's for my own understanding. ...
7
votes
2answers
164 views

Is there any recommended approach for “upgrading” MD5 hashes to something secure? [duplicate]

I'm currently dealing with a couple of user accounts containing MD5 hashed passwords. These accounts got migrated from an old system into our current system which uses PBKDF2 for password hashing. I ...
27
votes
3answers
4k views

Can I share what password hash function I used in a public report?

I have developed a web site during an internship, using a database with accounts. I used the crypt() method from PHP, with a secured algorithm plus salt (found on the web with a lot of feedback). ...
21
votes
4answers
18k views

Whats the difference between MAC vs hash

What is the difference between the two algorithms? One difference that I know of, is that MAC is keyed and hash is not.